1. Field of the Invention
The present invention relates to a welding apparatus assembled together with grinding device. More particularly, the present invention relates to a welding apparatus in a butt welding system for steel strip or steel plate which is particularly equipped with grinding device in one system.
2. Description of the Related Art
As conventional welding apparatuses for butt joint of steel strip or steel plate, LASER, plasma-are, MIC or TIG welding apparatuses have been known and commonly used. Such welding apparatuses may often generate excess metal or undercut at the welded joint, which may cause stress concentration at the irregular shaped welded joint resulting sometimes in rupture at the welded portion, when the steel strip or the steel plate is subjected to the passing step of process line such as annealing, heat treatment, pickling or so and/or rolling step in the succeeding process.
Thus, in conventional process, a grinding device is additionally arranged in the downstream of the welding unit. The welded joint is stopped at the grinding position of the grinding device to perform grinding for the welded section to be flush. This conventional process has needed to take about 100 seconds for performing grinding; i.e., for feeding the welded joint into the grinding apparatus, arranging the welded part with the center of the grinding wheel and finishing the grinding. This has remarkably lowered the efficiency of the continuous process line. Further, the grinding device should be additionally constructed, so that the construction cost for the process line will become high.
On the other hand, in order to perform upset butt welding and grinding for the excess metal of the welded joint at the same position, a specific device for grinding the excess metal by using a flush trimmer at the welding position has been proposed. (Refer to Japanese Patent Application Open Publication Nos. Sho. 51-121452 and 52-61143.) In this device, a shearing machine for cutting the ends of preceding plate and succeeding plate and a flush trimmer are arranged at one side of the welding apparatus. These shearing machine and the flush trimmer are inserted into the inner space of the welding apparatus when use. Clamping for grinding operation is carried out by means of a specially designed clamping device therefor or electrodes arranged at the inlet and outlet portion of the welding apparatus. Either requires an auxiliary clamping device, which has complicated structure to demand difficult operation procedure. Further, it is impossible to start the grinding operation until the welding operation along the whole width of the steel plate has been completed.
Although in conventional manner the welded section has been corrected by cutting with a cutting tool, such cutting operation can not completely remove the excess metal from the welded joint, especially when the two plates are different in their thickness. Additionally, conventional manner can not correct the undercut, so that this will cause various problems when the welded joint is subjected to rolling in the succeeding step.